Well TG 38.1-TG 38.3 in of December 1944 was 27- 28 ships consisting of 3-5 fleet/escort carrier mix and adjoining BB/CA and numerous destroyer escorts. These Task Groups and others at the time made up the 3rd Fleet which essentially was one big 132 ship fleet. I have also seen pictures of at least 20 carriers all sailing in the same fleet ( again carrier mix of fleet.cve ), in the closing stages of the war. Task Force 42 I think was one of the largest I believe? I don't think those Task Forces had any penalty's for over 20+ ships in RL tho! lol

Several discussions in AARs left conventional wisdom as recommending no more than 10ish for good surface combat fighting, although the official impacts are at 15 and 25 as stated. The 10 ship thing is anecdotal but seemed supported by the fact that ships in bigger TFs failed to engage often.

Even more important was TF composition. Matching speeds and, critically, main gun ranges for TF capital ships was demonstrably better per the collective wisdom, articulated best by Nemo's excellent posts on the matter.

I never really found matching gun size and speed were as critical as some do. As long as things are close I think it is OK. I have not seen any adverse effect in placing say six inch CLs in a TF with eight inch gunned CAs, or a 32 knot DD in a TF with a 36 knot DD. I do think TF size in a night action is important and really never use TFs larger than 10 ships if looking for a night fight. But there are many other factors. Moonlight is just a critical as TF size and composition. Anyone using BBs in a TF with little or no moonlight is just asking to eat torpedoes while perhaps the larger capital ships won't fire a shot in return. On the other hand, full moonlight might allow for an extra ship or two and generally opens the ranges making it more suitable for larger ships. And it depends on your goals. Smaller but multiple TFs may overwhelm a larger superior TF.

Most important this is you want every ship to fire its guns and torpedoes. This becomes less likely the larger a surface TF is.

Several discussions in AARs left conventional wisdom as recommending no more than 10ish for good surface combat fighting, although the official impacts are at 15 and 25 as stated. The 10 ship thing is anecdotal but seemed supported by the fact that ships in bigger TFs failed to engage often.

Yes, no point to put more than 10-12 ships to surface combat TF. One of my opponent tend to used 20-25 ships. Those TFs could do absolutely nothing.

One of my best combat TF was just 4 Japanese Fubuki-class destroyers. They sunk modern allied BB with Long Lances, and badly damaged heavy cruisers. It was night time combat with little moonlight. Eventually I lost 2 DDs.